Depression means as it says, prices for everything are depressed. Inflation is the exact opposite. You can’t have both at the same time.
There was severe depression in Germany that led to the rise of Hitler, but postage stamps went to millions and then billions of marks. In the US, the first class postage rate was two cents throughout the 1920s, and was raised to three cents in the middle of 1932.
I think you need to take an economics class.
ML/NJ